Circuit breakers are protective devices which operate like a fuse. Circuit breakers monitor the current flowing there-through via a conductor and interrupt the electric current/the energy flow to an energy sink/a consumer, which is called tripping, if protective parameters such as current limit values or current-timespan limit values are exceeded, wherein a current-timespan limit value is understood to mean a current value which is present for a certain timespan. Interruption is effected for example by way of circuit breaker contacts, which are opened.
In particular, for low-voltage circuits or networks various types of circuit breakers are known depending on the level of the provided electric current in the electric circuit. Circuit breakers in terms of the embodiments of the present application are in particular understood to be switches as used in low-voltage systems for currents from 63 to 6300 Ampere. In particular, closed circuit breakers are used for currents from 63 to 1600 Ampere, in particular from 125 to 630 or 1200 Ampere. Open circuit breakers are used in particular for currents from 630 to 6300 Ampere, more particularly from 1200 to 6300 Ampere.
Open circuit breakers are also called air circuit breakers, ACB for short, and closed circuit breakers are called molded case circuit breaker or compact circuit breaker, MCCB for short.
Low-voltage is understood to mean in particular voltages up to 1000 Volt alternating current or 1500 Volt direct current.
Circuit breakers in terms of the embodiments of the present application are understood, in particular, to mean circuit breakers with an electronic trip unit called ETU for short.
If current flow is excessively “high”, circuit breakers interrupt the circuit in accordance with their protective parameters or response values. The protective parameters/response values basically denote the level of the current and the time after which the circuit is to be interrupted if the current flow is continually “high”. In contrast to a fuse, these protective parameters/response values can be set for a circuit breaker, for example by way of the electronic trip unit. The trip unit is usually attached so that it is accessible via the front of the circuit breaker. The protective parameters can be set or parameterized via this trip unit. Often rotary encoding switches are used for setting the protective parameters/parameterization, and these are attached at the front of the electronic trip unit.
The protective parameters which can be set via these rotary encoding switches are those which decisively determine the trip times or/and trip currents. An inadvertent or deliberate alteration of these settings by unauthorized persons can have serious consequences for the protection of the electric circuit/the operated electrical system. It is, for example, possible that the required protection may have been undone leading to the destruction of system components.
In order to prevent changes to the protective parameters, a sealing pane is provided which covers at least part of the circuit breaker and, in particular, protects the rotary encoding switches against unauthorized access. A mechanical protection against changes to the protective parameters is thus realized. The sealing pane is secured by a seal.
An electronic trip unit may also be provided with a display and with communications ports such as CAN. Further a testing device, for example, may be connected. In the meantime, a change to the protective parameters can also be made via these interfaces. According to the state of the art a change to the protective parameters is secured in this case by a password.